Starting a filter-less reef system w/no lights

[Gregg @ ADP]

I’ve been wanting to put together some sort of reef system in my classroom since I moved into it, so I finally decided to put something together.

Space is somewhat limited, and I’ve already got a 170gal river system (more on that later). My room features 40’ of unobstructed south facing windows, and I’ve wanted to take advantage of that. Because I don’t have a ton of space, I decided to use 2 20gal tanks that I had lying around that were already drilled.

I teach biology and enviro sci, and because both classes spend a fair amount of time on ecology, I wanted to set up a system that had no filtration or artificial light. I had already set one of the tanks up as a shallow mangrove lagoon tank last year, and the mangroves have been growing nicely. My plan is to use the mangrove lagoon as nutrient management, and the good ol sun as the light source.

Here’s the set up so far:

The mangrove lagoon is set up with a DSB and a sort of under-gravel/plenum set up. The idea is to slowly pump water up from under the bed so that I am drawing more water over the roots of the mangroves (and turtle grass when it comes in) than what I could achieve by just having the plants in a static bed. This should result in more nutrient uptake.

There is a power-head on that system now, but it’s too much and is kind of compacted the sand bed a little. I’m going to change it to either air-pump or very small pump. I just want maybe 50gph going through the bed.

Now for the lighting. Early fall through late spring (or the bulk of the school year) the spot the tank is in averages 4-5hrs of direct sun, and by direct, I mean that I can open the windows and get direct unfiltered sunlight. But there are also a few hours of indirect but fairly bright light. There is also an hour or so in the early morning where low-angled direct light goes in from the east.

I realize my corals and reef will not look like a black-light poster, but I’m curious to see what some of these corals start to look like once they adjust to sunlight.

Anyway, I finally got the reef tank set up the other day. I’m debating between using the big sump I have underneath or just connecting the two tanks. Haven’t decided yet. The benefit of the sump would be that I could paint a portion of it black to make a dark cryptic zone for sponges, worms, etc.

So, no skimmer, no media, no mechanical filtration, no water changes, no artificial lighting…just nature at its finest. And oh yeah…top off water is going to come from my river tank.

What do you all think?

 

[Gregg @ ADP]

I will probably pull most or all of the rock that is currently in the lagoon out and just have turtle grass and maybe some lagoon corals and sponges.

The plenum-ish set up under the substrate is a piece of plastic egg-crate wrapped in plastic screen on top of some pieces of 1” pvc so that it is supported and doesn’t cave in. Then there is about 3” of substrate toward the front sloping up to 5” in the back. The substrate bed is med-large crushed coral pieces with a piece of screen over it, and then a layer of Miracle Mud with a little gardening soil and oolitic sand mixed in, with a layer of oolite over the top for aesthetics.

 

[livinlifeinBKK]

It's a cool idea but to support coral given the nitrates and phosphates the fish will produce do you really think the mangroves can export enough nutrients and at a reliable rate which is needed for good coral health and growth? Also, mangroves take up a lot of magnesium from what I've heard which the corals will also need, not to mention that if your phosphates and nitrates do happen to be elevated the natural sunlight will probably grow algae like crazy (or so I'd expect)...this will certainly be interesting though!

 

[Oldreefer44]

Will be interesting experiment. Also agree that algae will likely be a major issue so that nutrient export balance will be necessary in the long term.

 

[Gregg @ ADP]

It's a cool idea but to support coral given the nitrates and phosphates the fish will produce do you really think the mangroves can export enough nutrients and at a reliable rate which is needed for good coral health and growth? Also, mangroves take up a lot of magnesium from what I've heard which the corals will also need, not to mention that if your phosphates and nitrates do happen to be elevated the natural sunlight will probably grow algae like crazy (or so I'd expect)...this will certainly be interesting though!

Thanks for the reply.

The model I used for this is the river ecosystem I designed in the classroom. In the shallow end of the tank (which has some interesting modifications to allow for advection of water through the bed), I have irises and arrow-leaf plants growing in the same direct sunlight. The tank has 3 turtles and about 15-18 fish native to the area. The amount of food I put in that system is ridiculous compared to what a reef would get.

Even though it gets a ton of sunlight, there is almost no algae growth. The plants grow like crazy though.

When I first started the lagoon tank, I couldn’t get the mangroves to grow much. Eventually I started putting way more food in than the fish in the tank needed, and they started to grow pretty well. Will they alone be able to handle the nutrients when I quadruple the fish biomass? Probably not. That’s why I’m going to add turtle grass, which I can harvest out.

The coral itself will use the nitrogen and phosphorous for its own growth as well.

But that’s the main reason I’m considering a cryptic zone. Well, that, and if I design it properly, the students will be able to observe it.

Elemental uptake will definitely be something to watch/measure.

 

[Gregg @ ADP]

Should probably tag the usual suspects @Sallstrom @MnFish1 @brandon429 for their input

 

[brandon429]

That's beyond motivational to students who like science, animals and biology


Truly the setup there is orders beyond what my college biology lab had in the 90s and that was pretty top notch for landlocked west tx. You're able to showcase animal species diversity 99% of your students won't see outside your classroom is why it's impactful in my opinion. 1% or a tenth of one pct lol have parents with a reef tank: hey that's a cleaner shrimp! First kiddo that names an item and exclaims it out please give them brandon429 props

It's better than just having one giant reef tank; the multi ecosystem is classroom ideal in every way.

I believe the lighting intensity should directly factor the excellent indirect light; run lower than norm to keep algae at bay. The natural sunlight will help in every way possible its perfect

 

[Gregg @ ADP]

That's beyond motivational to students who like science, animals and biology


Truly the setup there is orders beyond what my college biology lab had in the 90s and that was pretty top notch for landlocked west tx. You're able to showcase animal species diversity 99% of your students won't see outside your classroom is why it's impactful in my opinion. 1% or a tenth of one pct lol have parents with a reef tank: hey that's a cleaner shrimp! First kiddo that names an item and exclaims it out please give them brandon429 props

It's better than just having one giant reef tank; the multi ecosystem is classroom ideal in every way.

I believe the lighting intensity should directly factor the excellent indirect light; run lower than norm to keep algae at bay. The natural sunlight will help in every way possible its

People have already brought up the issue of nutrients, and understandably.

One of the things I’m adding to the ecology part of the curriculum this year is bottom-up and top-down nutrient control. My thinking is that the bottom-up will be handled by two different processes…uptake from a) plants and algae, but also all other organisms like sponges, worms, coral, and the dinos in the coral, and b) anaerobic microbial breakdown as water flows through the deep sand. If I can get the advection down through the bed down to a low enough rate, the water should be anoxic before it goes all the way through.

Top-down will be handled by the usual suspects.

Also curious about whether or not we can get some calcium breakdown deeper in the bed as the CO2 increase and pH decreases.

We have a bunch of different probes that the students can measure that stuff with.

 

[Lowell Lemon]

Cool, I want to see how this develops!

 

[Nano sapiens]

I don't doubt that your plan can be successful. Since the system is intended to be a teaching tool for students, having mangroves, sea grass and a cryptic zone are fun add-ons and add to the interest and complexity of the micrcosm. Strictly speaking, though, none of that is actually necessary to run a successful reef aquarium.

It is quite possible to run a bare-bones 'simplistic' reef system with just a pump, heater, thermometer, live rock, relatively shallow live sand without a plenum or a DSB and light for photosynthetic organisms as are usually included. Quite fascinating to observe how such an initially simple system goes through many different phases as it develops towards ever greater stability and maturity over time.

 

[Gregg @ ADP]

I am notoriously bad about following up the threads I start, so I figured I would update how things are ‘progressing’.

For now, I have not connected the sump, but I want to because I have a bunch of ideas for it. So I simply connected the upper mangrove tank and the reef tank together for now via power head in the reef tank pumping up to the mangroves, and then draining back into the reef. I definitely want that to be temporary, because I hate the look of the power head in the tank.

As for populating the system, so far I’ve added:
1) Reef- green slimer, monti cap, random acro, bubble tip anemone, leptastrea, royal gramma, orange prawn goby
2) Mangrove- orange prawn goby w/pistol shrimp, Hector’s goby, cleaner shrimp, and random sand snails, hermits, etc.

The primary thing I’ve been curious about has been how these essentially aqua-cultured coral frags would adjust to sunlight. So far, so good. By that, I mean that nothing has died. They don’t appear to be stressed, but they don’t look amazing, so I’m just going to assume they’re adjusting. The anemone, on the other hand, really seems to like the sunlight. It bends toward it once the sunlight hits the tank.

I definitely need to add more animals. I’m adding far more food than I have animals to feed, but I’m still barely getting any algae growth at all. The mangroves are doing well, but it’s a struggle to get much algae growth. The mangroves are doing well and growing. The next thing I’m going to add is turtle grass for the mangrove/lagoon tank.

Here’s where it’s at right now:

Oops…just realized I don’t have any updated pics.

But here’s something cool…the pistol shrimp has dug a myriad of tunnels in the lagoon tank, and one of its tunnels goes right up to the front glass:

 

[Gregg @ ADP]

Another interesting thing I’ve noticed is the amount of gas that builds up under the ‘plenum’. About once a week, I pull the power head out of the PVC riser and blow water down the pipe and under the sand bed. Lots of gas gets trapped under it, and reversing the flow blows a lot of it up through the sand.

My assumption is that it is N2(g) from the anaerobic breakdown. I suppose I could always test the nitrates.

 

[Lowell Lemon]

Another interesting thing I’ve noticed is the amount of gas that builds up under the ‘plenum’. About once a week, I pull the power head out of the PVC riser and blow water down the pipe and under the sand bed. Lots of gas gets trapped under it, and reversing the flow blows a lot of it up through the sand.

My assumption is that it is N2(g) from the anaerobic breakdown. I suppose I could always test the nitrates.

You could try a low flow reverse undergravel filter like Subsea and Paul. In fact I want to try one myself. Looking great Gregg.

 

[Gregg @ ADP]

You could try a low flow reverse undergravel filter like Subsea and Paul. In fact I want to try one myself. Looking great Gregg.

I had considered that, but I think I’m going to stick with the downward flow. Just want to keep it as ‘natural’ as possible. The issue currently is that the powerhead is too strong, and that much advection is compacting the bed too much.

I am going to switch to an air stone down in the standpipe (super old fashioned UG filter), and add more sand sifters, burrowers, etc to keep the bed loose and maybe prevent some of the N2 gas build-up. At the end of the day, it’s not a big deal, because it’s easy to blow it out. And assuming it is N2, then I should have low N03…which would at least partially explain the very low algae growth so far.

 

[Gregg @ ADP]

And in keeping with my theme of ‘things that will drive this board nuts’, I am also only using straight tap water.

 

[Gregg @ ADP]

So this is how the system is currently looking:

Coral looks good and seems to have adjusted to the sunlight (in other words, it’s not dead). There is pretty good polyp extension on the acros. Color is adjusting.

The upper tank is showing about 2 weeks worth of algae growth. Pretty sparse growth despite putting 2x more food in the tank each day than what the animals can consume.

This week I’m adding-

Mangrove tank:
- turtle grass
- manatee grass
- maricultured live rock from Gulf Live Rock
- halimeda

Reef:
- a few more fish
- several frags (various montis, more acro, Seriatopora, Porites, etc)
- maricultured live rock
-can’t remember what else

For top-off water, I’ve decided to just pull water out of the river aquarium. Thinking that will kick the growth up.

 

[Gregg @ ADP]

Even though it’s not saltwater, here is the river system I have in my classroom. It’s the same concept…no ‘filtration’.

Around 20-25 fish, 3 green frog tadpoles, 3 different turtle species, crayfish, etc. Have a scientific collectors permit that allows me to keep the gamefish I have in there. There is a sump, but I really only use it to keep the water level in the tank. Completely cut one overflow box out, and cut the other one down about 5” from the top to set my water level. A pump circulating about 800gph, and then a flow pump for the river current.

It’s a 170 gal tank, but is probably at about 150 gal in the tank. It’s becoming one of my favorite tanks.

 

[Spare time]

I hesitate to run tanks without carbon due to hormones being released into the water and possibly creating issues when they linger

 

[Gregg @ ADP]

Is there an easy way to move a thread, or do I just have to start it over? I always forget there are build forums here.

 

[Gregg @ ADP]

This year, our 1st semester ends a couple of days before break, with our finals week starting 12/19. Students are done on 12/22. For some reason, we have a self-directed PD day on 12/23. Beyond some prep for semester 2, there won’t be much to do that day…for most teachers.

I’m going to use the day to redo my whole reef/lagoon set-up. The main project will be completing and hooking up the sump. But I’ve been assessing things I like and don’t like about the current set-up, which has the lagoon tank on top of the reef tank.

I want to lower the lagoon tank, and maybe just have the reef and lagoon right next to each other. I also want to lower the top shelf by at least a foot so that it’s easier to see into the tanks.

Ideally, I would just turn the shelves perpendicular to the window, but all of my class safety stuff/eye rinse sink/etc is in the part of the room, and it would be really difficult to get to it. So I have to make the current layout work somehow.

So far, I would say the corals are loving the sunlight. The frogspawns are in the lagoon tank, and they seem to be loving life:

Seeing some decent growth out of the SPS in the reef. They don’t glow in the dark, but all seem pretty happy. Here’s what a green slimer looks like in the sun rather than 460nm:

I’m still waiting for people to share hypotheses as to why corals will tweak so much at changing LED lighting, but going from LED to sunlight didn’t cause any stress or set-backs.